Augspurger N R, Baker D H
Department of Animal Science, University of Illinois, Urbana 61801, USA.
J Anim Sci. 2004 Apr;82(4):1100-7. doi: 10.2527/2004.8241100x.
Four trials investigated the effect of high levels of three phytase enzymes on P and protein utilization in chicks. The three phytases were derived from Aspergillus (Fungal Phytase 1), Peniophora (Fungal Phytase 2), and E. coli. Within each assay, 8-d-old male chicks were given ad libitum access to their experimental diet for 10 to 14 d. For Trials 1, 2, and 3, the basal diet was a corn-soybean meal diet deficient in P that was analyzed to contain 23% CP and 0.38% total P (0.10% estimated available P, as-fed basis). Phytase supplementation levels were based on the assessment of phytase premix activity (i.e., P release from Na phytate at pH 5.5 and 37 degrees C). In Trial 1, supplementation of inorganic P from KH2PO4 (0 to 0.20%) resulted in a quadratic (P < 0.05) response in weight gain, gain:feed, and tibia ash concentration but a linear (P < 0.01) increase in tibia ash weight. Tibia ash was higher (P < 0.01) for chicks fed E. coli phytase than for those fed Fungal Phytase 1 at 500, 1,000, and 5,000 phytase units (FTU)/kg, but did not differ between these two phytases at 10,000 FTU/kg. In Trial 2, E. coli phytase supplementation at 1,000 FTU/kg maximized growth and bone responses, whereas addition of either of the two fungal phytases resulted in increasing responses up to 5,000 and 10,000 FTU/kg. Dietary addition of Fungal Phytase 2 resulted in the poorest (P < 0.01) responses among the three phytases. Escherichia coli phytase supplementation at 10,000 FTU/kg in Trial 3 resulted in tibia ash (millligrams) responses that were greater (P < 0.05) than those resulting from either 0.35% inorganic P supplementation or 10,000 FTU/kg of Fungal Phytase 1 or 2. Trial 4 showed that E. coli phytase supplementation at either 500 or 10,000 FTU/ kg did not improve protein efficiency ratio (gain per unit of protein intake) of chicks fed low-protein soybean meal or corn gluten meal diets that were first-limiting in either methionine or lysine, respectively. These results demonstrate that high dietary levels of efficacious phytase enzymes can release most of the P from phytate, but they do not improve protein utilization.
四项试验研究了三种高剂量植酸酶对雏鸡磷和蛋白质利用率的影响。这三种植酸酶分别来源于曲霉（真菌植酸酶1）、卧孔菌（真菌植酸酶2）和大肠杆菌。在每项试验中，8日龄雄性雏鸡可随意采食试验日粮10至14天。试验1、2和3的基础日粮是一种低磷玉米-豆粕型日粮，分析其粗蛋白含量为23%，总磷含量为0.38%（估计有效磷含量为0.10%，以饲喂状态计）。植酸酶的添加水平基于对植酸酶预混料活性的评估（即，在pH 5.5和37℃条件下从植酸钠中释放的磷）。在试验1中，添加KH2PO4（0至0.20%）的无机磷导致体重增加、增重：采食量和胫骨骨灰分浓度呈二次曲线反应（P < 0.05），但胫骨骨灰分重量呈线性增加（P < 0.01）。在500、1000和5000植酸酶单位（FTU）/kg水平下，饲喂大肠杆菌植酸酶的雏鸡胫骨骨灰分含量高于饲喂真菌植酸酶1的雏鸡（P < 0.01），但在10000 FTU/kg水平下，这两种植酸酶之间无差异。在试验2中，添加1000 FTU/kg的大肠杆菌植酸酶可使生长和骨骼反应最大化，而添加两种真菌植酸酶中的任何一种，在5000和10000 FTU/kg水平下反应均增加。日粮中添加真菌植酸酶2导致的反应在三种植酸酶中最差（P < 0.01）。试验3中添加10000 FTU/kg的大肠杆菌植酸酶导致的胫骨骨灰分（毫克）反应大于添加0.35%无机磷或10000 FTU/kg的真菌植酸酶1或2所导致的反应（P < 0.05）。试验4表明，在分别以蛋氨酸或赖氨酸为第一限制氨基酸的低蛋白豆粕或玉米蛋白粉日粮中，添加500或10000 FTU/kg的大肠杆菌植酸酶并不能提高雏鸡的蛋白质效率比（每单位蛋白质摄入量的增重）。这些结果表明，高剂量的有效植酸酶可从植酸盐中释放出大部分磷，但不能提高蛋白质利用率。
